Talk about setUp and tearDown in the README.
Talk about setUp and tearDown in the README.

Closes #347

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1397903003 .

grouma/test,grouma/test,iglherme/Guttiest,iglherme/Guttiest,kevmoo/test,kevmoo/test,iglherme/Guttiest,grouma/test,kevmoo/test